There is a growing demand for small, random- or irregular-shaped die-cut blanks. For example, bottle labels and aluminum foil package lids with pull-tabs are two types of die-cut blanks that are very popular. These shapes are currently being die-cut by reciprocating die cutters either from stacked sheets or by intermittently web-fed reciprocating die cutters at average web speeds of 150 feet per minute (fpm) or less. Reciprocating die cutters have traditionally been particularly suitable for die-cutting irregular-shaped blanks because of their inherent capability to reliably and positively separate the die-cut blanks from surrounding sheet scrap or surrounding web matrix. In the die-cutting of stacked sheets, a hollow die can push the die-cut scrap away from the remaining stack of die-cut blanks, while in the die-cutting of intermittently fed web, the male die can push the blank through the female die. However, in both the die-cutting of stacked sheets and an intermittently fed web, the production speeds are quite slow.
On the other hand, present rotary die cutters can obtain high die-cutting operating speeds that are several times faster than intermittently web-fed reciprocating die cutters. However, rotary die cutters have an inherent incapacity to separate small and/or flexible material blanks from the scrap matrix web. Additionally, web-fed reciprocating die cutters have an inherent incapacity to prevent higher speed instability of the scrap matrix web from impeding the small blank delivery and thereby limiting the process speed.
Therefore, it is an object of the present invention to provide a web-fed, rotary die cutter that includes the enhanced capability of separating small and/or flexible material blanks from the scrap matrix web. It is a further object of the invention to provide a rotary die cutter that includes a die-cutting module that can replace a rectangular-label sheet cutting module in a high-speed web rotary slitting and sheeting machine. It is an additional object of the present invention to provide a rotary die cutter that can be operated at high web speeds while providing positive separation of the die-cut label blanks from the scrap matrix.
The present invention is a continuously web-fed rotary die cutter. As opposed to intermittently web-fed and sheet-fed reciprocating die cutters, continuously web-fed die cutters are particularly suitable for high-speed web production.
The rotary die cutter of the present invention includes a random-shaped die-cutting module that functions to die-cut labels of the desired size while providing positive separation of the die-cut label from the scrap web matrix. The die-cutting module includes a male die cylinder that has a series of die cavities positioned around its outer circumference. Each of the die cavities formed in the male die cylinder is surrounded by a cutting edge that defines the shape of the blank being die-cut from the continuously fed web.
The male die cylinder includes resilient elastomer pads positioned within each of the die cavities. The elastomer pad positioned within each of the die cavities interacts with either an anvil cylinder or a female die cylinder positioned adjacent to the male die cylinder to form a cutting nip. The continuous web of material travels around the outer circumference of the anvil cylinder or female die cylinder and enters into the cutting nip. The elastomer pad contained within each die cavity of the male die cylinder impresses against the outer circumference of the opposed anvil cylinder or female die cylinder.
Radial vacuum ports are provided for each die cavity along the outer circumference of the male die cylinder. The radial vacuum ports are coupled to a phased vacuum chamber such that a source of vacuum can be applied to the die-cut label blank to hold the label blank in contact with the elastomer pad formed within the die cavity. In this manner, the supply of vacuum and the elastomer pads provide positive separation of the die cut label blank from the scrap web matrix after the label blank has been die-cut by the male die cylinder.
After the label blank has been die-cut by the male die cylinder, the male die cylinder carries the label away from the cutting nip. Once the label has been transported to the desired position, the supply of vacuum within the male die cylinder is terminated such that the die-cut label blank is released from contact with the outer circumference of the male die cylinder.
The invention provides a novel way to reliably die-cut small irregular- or random-shaped blanks with positive separation and removal of the blanks from the scrap matrix web, and maintaining stable control of the scrap matrix web, thus making possible high-speed rotary die-cutting of small, irregular-shaped blanks from any web material. Further, the invention provides a module configuration of the die-cutting equipment that can be interchanged with the sheeting module of a small-rectangular-blank rotary sheeter, and a method to convert and utilize the rectangular blank rotary sheeter""s delivery section to stack the irregular-shaped die-cut blanks.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.